CHAPTER2

SYNTHESIS AND CHARECTERIZATION OF

Mn(II), Fe(II), Co(II), Cu(II), Zn(II) COMPLEXES

OF 3,5-DI NITRO BENZOIC ACID, CRYSTAL

STRUCTURES OF Co(II) AND Cu(II)

r •") Q i

r J ' .... ,

2.1 Introduction

The Mn, Fe, Co, Cu and Zn all are belonged in 1st transition metal senes

because the last electron in the atoms of these elements enters in d-sub-shell

belonging to penultimate shell. Most of the transition metals show more than one

oxidation states. Because of the presence of 'd' electron these transition metals

display different oxidation states and sometimes form complexes with the same ligand

in different oxidation state. This is generally true for the complex compounds of

transition metal chemistry and is a subject of interest for years due to not only of its

rich structural chemistry but also for its versatile applications. It is now well

recognized that in the human body minute amount of many elements can be detected

and estimated. Some of these elements have been shown to be essential for life. They

are involved in all major metabolic pathways of life. They serve a variety of functions

that include catalytic, structural and regulatory activities in which they interact with

various enzymes and biological membranes ( 1]. Iron functions as a cofactor for

enzymes mvolved in many metabolic processes, including oxygen transport, DNA

synthesis, electron transport and are transformed into biologically available fonn in

the mitochondrion by the iron-sulphur cluster and haeme synthesis pathway [2]. Zinc

plays an important roles in nucleic acid metabolism, cell replication, tissue repair and

growth. as well as zinc-containing nucleoproteins are involved in gene expression of

multiple proteins [3.4]. The Cu is present in the oxygen carrying system m blood of

many invertebrates and is a major constituent of many enzymes and proteins (5). The

Mn is an essential element to be found in all tissues. It is needed for metabolism of

amino acids, lipids, proteins and carbohydrates as well as it takes part in the defense

of red blood cells in the metabolism of iron [6]. It is well known that Co is an

essential metal necessary for the formation of vitamin B 12 [7]. The important role of

Mg in chlorophyll is well established in green plant system. But all the metals are

essential in small amounts; in large amounts, however, these may endanger the life

processes. Small amounts of Fe, Cu, Zn etc. arc found as growth and development

agents of fungi. Whereas, e.g, Cu and Zn when incorporated in some organic ligands

act as important fungicide. The (more toxic metals) Hg and Pb compounds can also

17

act as fungicides [8]. Further many transition metal complexes are associated with

biological and commercial applications [9-15].

2.2 Literature

Several cupric carboxylates are dimeric either in the crystalline state, in

solution or in both [ 16]. Considerable controversy has been caused over the mode of

bonding in the dimeric Cu(Il) acetate monohydrate [ 17]. The main cause of the

problem possibly arises from the method of preparation of the complexes. Frequently,

they are isolated as hydrates or solvates followed by dehydration under vacuum. The

application of heat to these complexes may cause slight decarboxylation of the

compounds affording anhydrous materials contaminated with small amounts of

copper oxide in insufficient quantities to affect the elemental analysis [ 18]. This

contamination of the complex would significantly affect the magnetic properties. So

the bonding mode of dim eric Cu(II) acetate is debatable [ 17]. Kumar and Suri [ 19]

have reported that the adducts of copper (II) aryl carboxylates with morpho line can be

prepared by interacting the reactants in 1: 1 molar ratio or using a large excess of

morpholin in acetone medium. Analytical results show that the adducts are either

mono-rnorpholine or bis-morpholine of l: l or 1 :2 stoichiometry formulated as

Cu(02CC6lf4Rb(morph)11 where R is H, CH3-o, CH 3-m, Cl-o, Cl-m, Br-o. Ch30-o,

Ch:;O-m. Ch30-p, NOro. N02-m, NOrp, OH-o, OH-m, and OCOCH,-o; Morph is

Morpholine and n is l or 2. Conductance measurements show that all these adduct are

non-ionic. Magnetic and electronic spectral studies suggest that mono-morpholin

adducts are dinuclear syn-syn carboxylate bridge spec1es whilst bis-morpholin

adducts are mononuclear distorted octahedral molecules. IR-spectra show that

morpholin behaves as a N-bonded monodentate ligand [19-20]. J. Bickley and his

coworkers [21) have described the synthesis and crystal structures of two new copper

complexes with chelating dicarboxylic acids. Reaction of copper(II) acetate with

diacid H2L2 (HOzCC(Me)20ArOC(Me)2C02H, Ar=l,3-substituted phenyl) gave a

bischelate complex (L2)2Cu2 • 2MeOH (Fig. 2.1) with the normal paddlewheel

structure and tilted, trans-oriented chelate rings with skewed conformations. The

overall structure was reasonably well reproduced by density functional calculations on

(L2)2Cu2. Treatment of the product from reaction of Cu2(0Ac)4 and diacid I-bL3

(AFc l ,3-substituted 2,4-dibromophenyl) with pyridine gave a six-coordinate

18

mononuclear chelate (L3)Py2Cu · H20 (Fig. 2.2) in which one chelate carboxylate ts

monodentate, the other is unsymmetrically bidentate and the pyridines are cis­

coordinated.

Fig. 2.1 Structure of(L2)2Cu2· 2MeOH [21].

0 Fig. 2.2 Structure of (L3 )Py2Cu· rhO [21].

In l99X. the dinucleating ligand N,N'-(2-hydroxy-5-methyl-l J-

xylylene)bis(N-(carboxymethyl)glycine) (Cf·hHXTA) has been used to synthesize the

dinuclear Cu(II) bis(pyridine) complex Na[Cu2(CH 3HXTA)(Py)2]" 1.5( I ,4-dioxane)

[Na(l )]: triclinic. The structure shows two distinct distorted square pyramidal Cu(II)

centers with each Cu(II) ion bound by two carboxylate oxygen atoms, one amine

nitrogen atom, a phenolate oxygen atom, and one pyridine nitrogen atom. The phenyl

ring of the CH 3HXTA ligand is twisted relative to the Cul-Ol-Cu2 plane, and the

resulting dihedral angle is 44.2°. The electronic absorption spectrum of 1 in aqueous

solution at pH 3 suggests a shitt toward trigonal bipyramidal Cu(Il) coordination in

19

solution. Spectral titration of Na[Cu2(CH3HXTA)(H20h] (Fig. 2.3) with L (where L-=c

pyridine or sodium cyanide) results in complexes with terminal L groups. These

exogenous ligands appear to bind in a positive cooperative stepwise fashion. Variable­

temperature magnetic susceptibility data for 1 indicate that the Cu(II) ions are

antiferromagnetically coupled (-2J = 168 cm- 1). The 1H NMR studies on a methanol

solution of 1 are consistent with weak spin-coupling in solution [22].

Fig. 2.3 Struch1re of[Cu2(CH3HXTA)(PyhT anion [22].

Akopova et a!. [23] described the synthesis, structure, and mesomorphism of

a new series of copper carboxylates la-f (Fig. 2.4 ). Compounds la,b,c,e were obtained

by fusing copper hydroxide with the corresponding acid, while compounds ld,f were

obtained by the exchange reaction. The influence of periphery of the chelate node on

the appearance of discophase was studied. A stacked hexagonal structure of copper

crucate was proved. The effect of restructuring of the chelate node in this compound

after its isothennic exposure, causing the loss of mesomorphism was revealed.

1a-t

20

c : R = -=-( Cl-h):> - COOCwH21

Fig. 2.4 Structure of copper carboxylate [23].

Kozlevcar et a!. [24] during the investigations of fatty acid copper(Il)

carboxylates with biologically important ligands prepared several compounds of the

composition [Cu2(02CCnH2n+1Murea)2] (n = 5 to 11) and [Cu2(02CCsH1 J)4(urea)2] .

The molecular structure of the compound [Cu2(02CC5H 11 )4(urea)2] (Fig. 2.5) was

determined by X-ray diffraction analysis. The compounds were characterized by

standard physical and chemicai methods and tested for their fungal mycelial growth

inhibition activity with mycelia of two wood decay fungi Trametes versicolor and

Antrodia millantii The results of the characterization are in agreement with the

values typical for dimeric copper(IT) carboxylates. In the electronic spectra the

difference between both types of hexanoate compounds was observed, however m

v1brational spectra also the differences among the compounds where one molecule of

urea is honded on each dimmer were noticed. Significantly higher growth mhibition

for the whole series for Antrodia vail!antii was observed.

Fig. 2.5 Structure of[Cm(02CC5H11 )4(0CN2H4)2) [24].

'Jl .1. ••

Waizump et al. [25] have reported the synthesis and crystal structures of

[Co(nic)2(H20)4] (1). [Co(isoh(H20)4] (2). [Cu(nich(H20)4] (3), and

[Cu(iso)2(H20)4] (4) (nic =nicotinate; iso ~· isonicotinate) (Fig. 2.6). The crystal of

complex 1 is monoclinic, space group C2/m and the other crystals 2 3 and 4 are all

triclinic. The arrangements around the metal ions are trans-octahedra with two pyridyl

nitrogen and two aqua oxygen in the equatorial positions and two aqua oxygen in the

axial positions, although the Cu(II) complexes show a larger Jahn-Teller distortion.

Complex 1

Complex 2

Complex 3

Complex 4

Fig. 2.6 Crystal structures of[Co(nic)2(H20)4] (1). [Co(isoh(H20)4] (2). [Cu(nic)2(lf20)4] (3) and [Cu(iso)2(H20)4] (4) (nic ---nicotinate; iso --- isonicotinate) [25].

2.2

Very recently, a Chinese group has synthesized a new complex,

Co(MBTC)2(DMF)2 (MBTC' !6-methoxybenzothiazole-2-carboxylate, DMF::JN,N­

dime- thylformamide), in DMF solution and characterized by single crystal X-ray

diffraction analysis. Using the cobalt complex as catalyst, phenylacetic acid was

prepared by the carbonylation of benzyl chloride with carbon monoxide (0.1 MPa).

The effects of solvents, phase transfer catalysts and temperature on the reactions were

investigated. The yield of phenylacetic acid was higher than 90% in optimized

conditions [26]. Vuckovic et a!. [27] reported novel binuclear Co(II) complexes with

N- functi onalized cyclam, N,N',N"',N'' '-tetrakis (2-pyridylmethyl)

tetraazacyclotetradecane (tpmc) and one of the aromatic mono or dicarboxylato

ligands (benzoate, phthalate or isophthalate ions). The compounds were analyzed and

studied by elemental analyses (C, H, N), electrical conductivities, VIS and IR

spectroscopy and magnetic as well as cyclic voltammetric measurements. In

[Co2(C6H,C00htpmc](Cl04h·3H20 (Fig. 2.7). the benzoate ligands are most

probably coordinated as chelates in the trans-position to each Co(ll) and the

macrocycle adopts a chair conformation. In the complexes

[Co2(Y)tpmc](Cl04)z·zH20, (Y '= phthalate or i-phthalate dianizon, z 2; 4), it is

proposed that the isomeric dicarboxylates are bonded combined as bndges and

chelates. The composition and the assumed geometries of the complexes are

compared with the, earlier reported. corresponding Cu(Il) complexes. Cyclic

voltammetry measurements showed that the compounds are electrochemically stable.

Fig. 2.7 Suggested structure of the [Co2(C<Jl,C00htpmc] 2 f- from complex (I) in a

chair conformation [27].

23

T. A. Zevaco and his coworkers [28] m 1998, have published a paper

covering the synthesis, spectral characterization and X-ray structure determination of

the zinc( II) norbomen-2,3 dicarboxylate [Zn(cis-2,3-ndc )-(1-

methylimidazole )2(Hz0)lrc (1) (cis-2,3-ndc = bicyclo[2,2, 1 ]-hept-5-ene-2,3-cis­

dicarboxylic acid). It crystallizes in the monoclinic space group P2 1/c. The crystal

structure of 1 consists of polymeric chains which propagate along the c axis. The

structure is stabilized by extended hydrogen bonds involving adjacent chains and

water molecules. The metal centers display a slightly distorted tetrahedral geometry

The norbomenedicarboxylic acid acts as a syn-bound 0,0'-bridging ligand. In the

same year they also published another paper which was covering the reaction of an

aqueous suspension of zinc oxide with 2-quinolinecarboxylic acid afforded, after

recrystallization from a 1-methylimidazole/ acetonitrile solution, crystals of the

anhydrous carboxylate LZn(2-quinoiinecarboxylato)z (1-methylimidazo!eh]. 1

[Zn(C10Hr,N02h (C4H6N 2)2], monoclinic, space group P2tln. The zinc atom Js

hexacoordinated, located at an inversion center and exhibits a slightly distorted

ctahedral geometry. The Zn-equatorial ligand distances arc 2.057(2) A for Zn---0 and

2.244(2) A for Zn---N. The Zn---N distance for the apical imidazole ligands is

2.144(2) A[29]

Hamed et a!. f 301 have reported that the compounds having the general

formula:Kn[M(F0h(H 20h] -xlbO, where (M cc Cu(Il) or Fe(III), n = 2 or I , FO =­

folate anion, x = 2 or 3 with respect) (Fig. 2.8), could be prepared and their absorption

efficiency in rodent's blood was determined. The obtained compounds were

characterized by elemental analysis. infrared as well as thermogravimetric analysis

and polarization of light The results suggest that the two folate complexes were

formed in 1:2 molar ratio (metal:folic acid) which acted as a bidentate ligand through

both carboxylic groups. Polarization of light proved that the folate complexes have

symmetric geometry.

24

Hi--1

', '.,H~ ~·,

:.:..'.' ; n.-: i ,· :.............-... ~1 ,'>1

,;!

1 / ~

,1)!'111!__,) .:~. \~)"r' 1.1 UH: (_I

Y. M. Trukhan and his coworkers [31] have reported that the reaction of the

new pol ydentate ligand 2,6-bis { 3-[ N,N-di(2-pyridylmethyl)amino ]propoxy} benzoic

acid (LH) with Fe(Cl04)3 followed by addition of chloroacetic acid leads to the

formation of the tetranuclear complex [{Fe20L(ClCH2-C02) 2 }2](Cl04) 4 (Fig. 2.9), the

crystal structure of which reveals that it consists of two Fe11 2()l-O)(JJ.-RCO~h cores

linked via the two L ligands in a helical structure. with the carboxylate moieties of the

two ligands formmg a hydrogen-bonded pair at the center of the helix.

Ghattas et a!. [32] prepared a p-oxo-diiron(III) complex bridged hy two

molecules of 1-aminocyclopropane- I -carboxylic acid (A CCII) that was prepared with

the ligand 1 ,4.7 -triazacyclononane (T ACN): [(T ACN)FeAp-O)(p-ACCl-1 )2l(CI04)4

2H20 ( 1) (Fig. 2.1 0). This complex was characterized, and its crystal structure was

25

solved. The bridging ammo acid moieties were found in their zwitterionic forms

(noted as ACCH). Reactivity assays were performed in the presence of hydrogen

peroxide and 1 turned out to be the first example of a well-characterized iron-ACCH

complex able to produce ethylene from the bound ACCH moiety.

~t"Dt ;i) -,;~; id'' ''" .,,•t\ ·, NJ,c "":·', ,. '.

v' ( CX'.

' " :/;:.· .~ ..6 ,~·- :~; . .,..

l'<' 00 '.;. l 0"

.,.. '

t~:

Fig. 2.10 Stmcture ofthe cation [Fe2(TACNhCu-0)(;t-ACCHh]4+ [32].

C M Grant and his coworker [33] have carried out a reaction between FeCh,

Na02CPh and L [L "'1,2-bis(2,2'-bipyridyl-6-yl)ethane] in MeCN that gave the

complex fFe(,()4Cl4(0:CPh)4L2][FeC14b 1 whose cation contains an unusual [Fe6(~t;-

0)4]H>+ core, whereas m MeOH the dinuclear complex [Fe~(OMe)r

Ch(OcCPh)L ][FeCI4] 2 was obtained; magnetic studies indicate that the cations of 1

(Fig. 2 1 I) and 2 (Fig. 2.12) both have S = 0 ground states, consistent with the

expected antiferromagnetic exchange interactions.

:: ,·""".~

Jl¥:'"-l--~..-~:-~&-.;&..-@f~tr"'· .,, ... ,.

Fig. 2.11 Structure ofthe cation of 1 [33].

26

Fig. 2.12 Structure ofthe cation of2 [33].

Moon et al. [34] have prepared the dinuclear Mn(Il) complex,

[Mn2(Hbida)2(H20)2] (Fig. 2.13 ), usmg a tetradentate tripodal ligand, N­

(benzimidaznl-2-ylmethyl)iminodiacetic acid (H 3bida) which has two carboxylate and i

one benzimidazole groups. The manganese ions are doubly bridged usmg f.!,ll -

bridging monodentate carboxylate oxygen atoms. The Mn~Mn bond distance of

1.446 A in this complex. The geometry of the complex is with four carboxylates in

tw0 ditferent types of binding modes, non-bridging monodentatc and fl·ll 1-type

bridging monodentate. The magnetic properties of the complex show a coupling

constant of J-cc ~oA 71 ( l) em 1, which 1s consistent with weakly coupled

anti ferromagnetic Mn11 (S = 5/2) centers.

Fig. 2.13 The graphical structure of[Mn2(Hbidah(Hz0)2] [34].

17 Ll

Maryudi et a!. [35] have reported a method of synthesis of manganese

carboxylates and their characterization. The ne\V method involves reaction between

molten carboxylic acid with sodium hydroxide in alcoholic solution to produce

sodium carboxylates and continued by reacting sodium carboxylate with chloride salt

of manganese. 1st and 2nd both step of reactions were conducted at 80-85°C and under

perfect agitation. 2nd step of reaction took place well in the low concentration of

manganese chloride, about 0.25 M or less. Thennogravimetric Analyzer test have

been done and the results obtained in this study have exposed the capacity of

manganese carboxylates stability at processing temperature of polyethylene.

Reaction of Fe(02CCH3)2 or Mn(02CCH3)2.4H20 with bidentate nitrogen

donor ligands affords the trinuclear complexes [M3(02CCH3) 6L2] [M=Fe, L=BIPhMe

(i) (Fig. 2.14); :M= Mn, L=BIPhMe (2) (Fig. 2.15) or 1,10-phenanthroline (3)] in high

yields. As judged from X-ray diffraction studies, these complexes adopt a novel linear

structure. with one monodentate and two bidentate bridging carboxylates spanning

each pair of metal atoms. Within this motif there are two geometric isomers that exist.

destgnated "'syn'' or '"anti" depending upon the mientation of the bidentatc nitrogen

donor ligands wtth respect to one another across the plane defined by the three metal

atoms and the two monodentate bridging oxygen atoms. Stmctural characterization of

thre~: Isomers of compound 2 revealed a considerable degree of flexibility in the

tricarboxylate-bridged dimetallic unit, with M-M distances ranging from 3.370 (3) to

3.715 (2) A [36].

28

Fig. 2.15 Structure of [Mn3(02CCH3)6(BIPhMe )2]"2CH2Cb, anti-2A [36).

Thermal decomposition of transition metal malonates, MCH2C204· xHzO and

transition metal succinates, M(CH2)2C20 4· xH20 (M=Mn, Fe, Co, Ni, Cu & Zn) have

been studied employing TG, DTG, DTA, XRD, SEM, lR and Mossbauer

spectroscopic techniques by Randhawa et al. [37). After dehydration, the anhydrous

metal malonates and succinates decomposed directly to their respective metal oxides

in the temperature ranges 31 0-400°C and 400-525°C respectively. The oxides

obtamed have been found to be nanosized. The thermal stability of succinates was

observed to be higher than that of the respective malonates [3 7].

Few complexes of Fe (III), Co (II), Ni (II) and Cu (II) with uracil, 6-amino

uracil and those with substituted phenyl azo-6-amino uracils containing o-methyl,p­

carboxy and o-carboxy subtituents and S.S -diety! barbitunc acid sodium salt have

been synthesized and characterized by elemental analys1s, magnetic moment and

spectral measurements(IR, UV-Vis, ESR). The IR spectra showed that uracil existed

in keto-enol tautomerism but 6-amino uracil possessed the kito amino-imine structure

with some enol form. The iron complexes were with octahedral geometries. The

square planar copper complexes existed in ligand bridged structures. The nickel

complexes were of tetrahedral configuration. In general, the azo group was involved

in the structural chemistry of the complexes. The coordination bond length was

calculated. The thcnnal propctties (TG and DT A) of the complexes were measured

and discussed and thermodynamic parameters were also evaluated [38].

29

A. Golobic and his coworkers [39] applied different synthetic routes for

preparation of some copper(II) carboxylates with 3-hydroxypyridine (3-pyOH). The

monomeric and dimeric complex of copper(II) acetate were isolated,

[Cu(02CCH3)2(3-pyOH)2], 1, and [Cu2(02CCH3)4(3-pyOHh], 2, respectively. A

covalently linked 2D Cull compounds of general formula (Cu(02CR)2(3-pyOH)2]n,

were prepared with benzoate (R=C6H5, 3), hexanoate (R=CH3(CH2)4, 4), and

heptanoate (R=CH3(CH2) 5, 5) ligands. The crystal structures of all five compounds

were determined by X-ray structure analysis. The compounds were tested for

fungicidal activity against two fungal species Trametes versicolor and Antrodia

vaillantii. Complete growth retardation for Antrodia vaillantii was noticed for

compounds 3, 4, and 5 at concentrations of 5 ·10-3 mol L- 1, 1·10·3 mol L-1

, and 5 ·10-4

mol L- 1, while in the case of Trametes versicolor complete growth retardation was

observed for the same three compounds only at the highest tested concentration.

Kozlevcar eta/. [40] synthesized and characterized a series of compounds of

the composition [Cuz(OOCC,H2n. i ) 4(niah] ( nia =nicotinamide; n -~ 6 to 11) and also

tested for fungicidal activity. Crystal structure determinations revealed dinuclear

structures of the copper(II) acetate hydrate type for compounds

fCuc(OOCC6H1-,)4(niah]-A ( lA). (Cu2(00CC6Hu)4(nia)2j-B (lB) and

!Cu2(00CCxH17Mniah] (3). Other applied characterization methods indicate dirneric

structures for all synthesized compounds [!-letT (298 K) = 1.43-1.50 BM; characteristic

band in tJV-Vis spectra in the region ~- = 150-400 nml. The same conclusion may

also be deduced from theIR (f\. =v3 ,1111

(COO )-Vsym(COO) = 183-189 em-!) and EPR

spectra. though some differences were observed for heptanoate modification 1A,

probably due to a different hydrogen bonding scheme. Screening for fungicidal

activity against the wood-rotting fungus Trametes versicolor ( L. ex Fr.) Pilat shows

that the compounds dissolved in DMSO completely stop mycelium growth at a

concentration of 1.0 x 10 3 molL 1. Some ofthem (n = 8, 9, 10) show strong activity

also in more diluted solutions (1.0 x 10-4 mol L- 1).

S. Shahzadi and his coworkers [ 41] synthesized transition metal carboxylates,

t.e., 3-[(2,4,6-trichloroanilino )carbonyl]prop-2-enoicacid and 3-[ ( 4-bromoanilino)

carbonyl] prop-2-enoic acid. The unimolar and bimolar substituted products have

been characterized by elemental analysis, IR, UV-Vis spectroscopy, 1H NMR, and

30

atomic absorption. IR data show the bidentate nature of the carboxylate group. The

transition metal complexes were tested in vitro against a number of microorganisms to

assess their biocidal properties.

2.3 Scope and objective

Carboxylates are ligands which contain 0 atoms as donors. In case of the

dinitrobenzoic acid the nitro groups may also act as donors through the 0 and N

atoms. Hence the acid as a ligand might be useful for complex formation. Therefore.

the ligand was chosen to examine its complex forming ability with transition metals

as a model and then to examine their fungitoxicity. Many transition metal compounds

[39-43] are known to be potentia! fungicides.

2.4 Experimental

2.4.1 General Comments

The solvents used in reactions were of AR grade and were obtained from

commercial sources (Merck, IndiaL The solvents were dried using standard literature

prLKCdurcs \Vater were distilled with sodium hydroxide and potassium permanganate

where as methanol was distilled after reacting it with solid iodine and magnesium.

2.4.2 Materials

The 3.5-di nitro benzoic acid (s.d.fine-chem limited, India), CuSC}r5H20

(s.d.fine-chem limited. India). CnC!o-6H 20 (Merck, India). FeS04 ·7H20 (s.d.fine­

chem limited, India). ZnS04·7H20 (s.d.tine-chcm limited, India), MnCh-4fh0

(Merck, India) of AR quality were used as received from commercial sources.

Methanol (Merck, India) used in the reaction was of AR grade.

2.4.3 Measurements

The IR spectra in the range 4000-400 cm· 1 were recorded on FTIR-8300

Shimadzu spectrophotometer with samples investigated with KBr on Csl window.

UV/VIS spectra were recorded on JASCO V-530. Microanalyses were performed at

31

the ICAS, Kolkata. India. Magnetic susceptibility was measured at room temperature

on a PAR 155 sample vibrating magnetometer using Hg[Co(SCN)4] as the calibrate.

Differential calorimetric analyses were carried out on a Perkin-Elmer Thermal

analyzer from l 00-230°C at a heating rate of 1 0°C/min. Metals were estimated using

standard methods in our laboratory.

2.4.4 Synthetic procedures

2.4.4.1 Preparation of sodium salt of 3,5-dinitro benzoic acid (LNa)

To a solution (40 ml) of 3,5-dinitro benzoic acid (4.0g, 18.85 mmol) was

added drop wise with continuous stirring NaOH (0.75g, 18.85 mmol) solution in

water (20 ml) in the presence of phenolphthalein as an indicator. The reaction system

was stirred for half an hour. Solvents removed by evaporation, leaving behind the

crystallized product of sodium salt of 3,5-dinitro benzoic acid. Then the sodium salt

was further recrystallized in methanol and dried in vacuo

LNa: Yield: 3.15 g; 78.75 %; M.P.: >240°C (dec).

Calcd.: C, 35.91, H. 1.2Y; N. 11.97 ryo.

Found: C. 35.82; H. 1.20; N, 11.94%.

IR (em·\ v(OCO)asym· l620(m); v(OCO)syn" 1459 (s); v(N02)as}1ll• I 534(111).

v(N02)syn" !345(m).

2.4.4.2 Preparation of Mn(ll) complex of 3,5-dinitro benzoic acid (1)

Sodium salt of 3,5-dinitro benzoic acid ( l.l8g, 5.05 mmol) was dissolved in

water ( 4 ml) methanol ( 120 ml) mixture and the solution was taken in 250 ml round

bottomed flask. The MnCh·4H20 (0.5g, 2.52 mmol) was dissolved in methanol ( l 0

ml) and added drop wise to the sodium salt of the acid. The mixture was then heated

under reflux for I Oh. The brown volatiles were removed from reaction mixture and

32

the dry mass washed with hot methanol and the brownish solid of desired product was

obtained by filtration which was dried in vacuo.

2.4.4.3 Preparation of Fe(II) complex of 3,5-dinitro benzoic acid (2)

Sodium salt of 3,5-dinitro benzoic acid (1.68g, 7.19 mmol) was dissolved in

water (4 ml) methanol (130 ml) mixture and the solution was placed in 250 ml round

bottomed flask. The FeS04 ·7H20 (l.Og, 3.59 mmol) was dissolved in methanol (15

ml) and added drop wise to the sodium salt of the acid. The colour of the mixture

turned to deep chocolate and a precipitate appeared. The mixture was heated under

reflux for 6h. Desired product as a reddish brown precipitate was obtained by

filtration_ The product was washed with hot methanol and dried in vacuo.

2.4.4.4 Preparation of Co(II) complex of 3,5-dinitro benzoic acid (3)

Sodium salt of 3,5-dinitro benzoic acid (0.98g, 4.20 mmol) was dissolved in

water (3 ml) methanol ( 140 ml) mixture and the solution was placed in 250 ml round

bottomed flask. The CoCh·6H20 (0.5g, 2.10 mmol) was dissolved in methanol (15

ml) and purple solution was added drop wise to the sodium salt of the acid. The

colour of the mixture turned pink after addition was complete. The solution was then

heated under reflux for 6h. Pink crystals of the desired product was obtained from the

filtrate after 25 days on slow evaporation, at room temperature.

2.4.4.5 Preparation of Cu(Il) complex of 3,5-dinitro benzoic acid (4)

Sodium salt of 3.5-dinitro benzoic acid (0_94g, 4.00 mmol) was dissolved in

water (3 ml) methanol ( 130 ml) mixture and the solution was placed in 250 ml round

bottomed flask. The CuS04·5H 20 (0.5g, 2.00 mmol) was dissolved in methanol (20

ml) and the blue solution was added drop wise to the sodium salt of the acid. After

addition the colour of the mixture became intense blue. The solution was then heated

under reflux for 6 h and then filtered. The filtrate was concentrated to a volume of 40

ml. Deep blue crystals of the desired product were obtained by slow cooling of the

solution.

33

2.4.4.6 Preparation of Zn(II) complex of 3,5-dinitro benzoic acid (5)

Sodium salt of 3,5-dinitro benzoic acid (0.81 g, 3.4 7 mmol) was dissolved in

water (3 ml) methanol (120 ml) mixture and the solution was placed in a 250 ml

round bottomed flask. The ZnS04 · 7H20 (0.5g, 1. 73 mmol) dissolved in methanol (15

ml) was added drop wise to the sodium salt of the acid. Then little amount of white

precipitate was appeared. The mixture was the heated under reflux for 6h and then

filtered. The filtrate was concentrated to a volume of 40 mi. White crystals of the

desired product were obtained by slow cooling of the solution.

2.4.5 Crystal structure determinations

The crystals of 3 and 4 suitable for the X-ray diffraction study were prepared

by slow crystallization of methanol solution of the respective compounds, the

crystallographic analysis of compounds showed the sample had crystallized as

methanol solvate. Intensity data were measured for selected crystals of 3 and 4 at 293

K on a Bruker SMART APEX diffractometer with fine-focus sealed graphite tube

with MoKet radiation, lc=- 0. 7107 J A so that 8max ~ 27.5° The data set was corrected

for absorption based on multiple scans [ 44]. Each structure was solved by SHELXS-

97 [45] and refined by a full-matnx least-squares procedure SHELXL-97 [45] on F2

with primary atom site location: structure- invariant direct methods, with hydrogen

atoms treated by a mixture of independent and constrained refinement and using a

weighting scheme of the form w'= ll[a2(F})+ (0.0522P)2 1- 0.1427 P] where P = (F0

2

+ 2F})!3. For compound 3 carbon-bound H-atoms were placed in calculated positions

(C H 0.9.1 to 0.96 A ) and were included in the retincmcnl 111 the nding mode:

approximation. with Uiso(H) set to 1.2 to I 5 Uequiv((') rhe methanol!! atoms were

located in a difference Fourier map, and were refined with a distance restramt of 0--l I

0.85±0.0 I A; their Uiso values were freely refined. The molecular structures showing

crystallographic numbering schemes were drawn with 501Yt> displacement ellipsoids

using ORTEP-3 [46] and diagrams were generated with the aid of the DIAMOND

programmer [ 4 7].

34

2.4.6 Crystallographic data and refinement details for 3 and 4

Crystallographic data and refinement details for 3

f-------------------+----------~-- --j Formula weight 609.33 J

~t--C-ry-s-ta_l_h-ab-i-t,-c-o-lo_u_r_~=--------~~---------~--~===:==P=r-t_·s=m=,=p=in=k====------_-_-_-_-_-_-~~~~--·~ j Ctystal system I Triclinic , r------ -------~----~-----~~- ~~----t· -~~--~------~ -~~~~-- -~1 I Space group 1 P I ~---------------

1 :~~ ------·~······~· ..... -r:~::~:;~ ~) i 12.1603(16)

t_~-a_-(_--0_)-~--~=~-~==----~--~----~~---~~=--~---~-~- ~-+~-9-0_.4_1_1 (-2-) ----~:~---_~~~---=--~-~~: I P(0

) 1 100.407(2) -~---;~-) ---- --~--~------------- ~- ------ --r---- 1 02.214(2)

-~ t

! 655.77(14) -- +------~--~-~--~---~

z ! l ~~-~-· -+----~-----~

j 1.543 -~--- - ~- -~ . ~ ------- ~ ~--~+-~-------~·--- -~

f,(MoKa,A} i 0.71073 - -~--~~--~~ ~- - ~-~-~--- ~--~ ~~-~-~ ~ ~~+---~- ~~--

F(OOO) ! 313 :· cr;_,;a·l·~;e (~~)·---------- - ------- I 0.35 X 0.3·(~)-~-0.05 __ _

~~ -Ab~~~ti~~~-~~~dfi~i~~;~~~(~m- 1 ) l o.74 -! e range for data collection (0 ) ---- ---~-------r-2.4-22~8·-- -------1 - ------.~-~~~- ~----·-- --------~~ ~- . ~ --l- ~-·---·-~·~-

! Reflection collected I 6372

r·-~;~d~pendent reflection i 2"999 ___ ~ --------··-----~- ~ --··--- - ----~- -~

0.028 f--------------------l--------~-------------·------~---

Reflection with I> 2cr(/) 2388 ·---·-

Number of parameters 188

0.043 f---------------~-~~~-----~- ----+-------~

~ wR(F

2

)_ .-~---- _ . ·. ..... .. . . .... +~~~~,( . _ ~~=: ~---L

Largest difference peak and hole (k3) 0.38

------ -------~-------··---· -··-· --- - _____ .....t______ -~-· ----

35

2.4. 7 Biological studies

2.4. 7.1 Antifungal activity

The virulent fungal strains of Lasiodiplodia theobromae and Cruvularia

eragrostidis were collected from the type culture collection, Dr. A. Saha, Depertment

of Botany, University of North Bengal. The strains were isolated from L. theobromae

(a pathogen of mango, Magnifera indica ) and C. eragrostidis (a pathogen of tea,

Camellia sinensis ). These strains were grown on potato- dextrose agar (PDA

HiMedia, India) medium at 27°C. The fungicidal activities were determined followmg

spore germination bioassay as described by Rouxel et a/.[48]. Purified eluants (151-11)

were placed on two spots 3 ern apart on a clean grooved slide. One drop of spore

suspension (15,.!1), which was prepared from 15 day old cultures of the fungi, was

added to the treated spots. The slides were incubated in trays at 27°C for 24h under

humid conditions. After incubation, one drop of Lactophenol mixture was added to

each spot to fix the germinated spores. The number of spore gennination events was

compared with the spore germination of the controL

2.4. 7.2 Phytototoxic effect

Seeds of fndian rice (Orvzae sativa), cultivar Khitish were collected from the

Directorate of Farm, Uttar Banga Krishi Viswavidyalaya, Cooch Behar, West BengaL

India. Seeds were first surface sterilized with 0.1% mercuric chloride for 3 min,

washed with distilled water and then the phytotoxic effects of the transition metal

carboxylates (dissolved in 2 ml methanol then diluted with 10 ml water) were

determined f 49). Seeds were incubated with different concentration of transition

metal carboxylates for different time periods. After incubation, the seeds were

washed with distilled water and incubated in a B.O.D. incubator for 48h at 27"C. The

percentage of seed germination was calculated and compared with the control.

2.5 Result and discussion

2.5.1 Preparation of sodium salt of 3,5-dinitrobenzoic acid

Sodium salt of the 3,5-dinitrobenzoic acid was prepared by neutralization with

equimolar aquous solution of sodium hydroxide. The sodium salt of the 3,5-

36

dinitrobenzoic acid was obtained in good yield. The product was recrystallized from

water/ethanol mixture. The ligand was soluble in water, water/ethanol and

water/methanol mixture. The ligand had a decomposition temperature at> 240°C. The

synthetic detail and characterization data for LH and LNa are described in section

2.4.4.1. The formula of the ligand and the abbreviations of the complexes are

presented in scheme 2.1.

0

1. [Mn(L)2 (CH30H)4j; 2. [Fe(Lh (CH30H)4]; 3. [Co(L)l. (CH30H)4];

4. [Cu2(L)4 · Cu(Lh · (CH,OH)]; 5. [Zn(Lh (CH;OH)4]

Scheme 2.1

2.5.2. Synthesis of transition metal(ll) complexes of 3,5-dinitrobenzoic acid (LH)

The transition metal carboxylates of \,5-dinitrobcnzuic acid ( M· Mn. Fe. Co.

Cu and Zn) were obtamed in moderate yields (except for Mn-carboxylate) by the l :2

reaction of transition metal sulfates/chlorides with the sodium salt of the ligand 111

water/methanol mixture as solvent for retluxation (Eq. 1 and Eq. 2). The sodium salt

of the ligand was generated by the addition of aqua's solution of NaOH to the aquous

solution of 3.5-dimtrobcnzoic acid. The reactions \'-'CIT comrlctcd !11 I Oh time Thl·

cornplexc-. produced are neutral chelated types. These are <llr stable tor 4gh because

bonding solvents arc released. The synthetic methodologies arc described in scheme

2.2.

LH + NaOH

LNa + MCb/MS04 ...

37

o-

0 + J\.;Cl2 I MS04

~ ~ 0

' C}--l\f--0

~ 0

1. [Mn(Lh (CH,OH)4]; 2. [Fe(Lb (Cth0H)4]; 3. [Co(L)2 (Cl-bOH)4j;

4. [Cu2(l)4 C:u(Lh · (CH:,OH)J; 5. [Zn(L)2 (CH30H)4]

Scheme 2.2

2.5.3 Spectroscopic characterization and X-ray crystal structure determination

of transition metal carboxylates, M(Lh [ where M= Mn, Fe, Co, Cu and Zn~

L=3,5-dinitrobenzoic acid]

The complexes were characterized by UV, IR and elemental analys1s

Magnetic moment data further suggested the composition of the complexes a:-,

proposed The composition nf the complexes. however <trc mainly hascd upt•n til,

elemental analyses supported by the spectroscop1c and other data where avallahk' ,,,

far as practicable 111 our laboratory conditions. In general, the X-ray crystallograp11ll

data of the complexes ( e.g.,3 and 4) supports the observed spectral and magnetic

moment data. Table 2.1 contains the relevant physical data of the compounds.

Table 2.1. Physical and analytical data for 1-5.

Composition Yield(%) Colour

1.

Elemental composition found (calcd) (%)

c H N M

30 I

Started Pale- 35.48 3.62 9.22 I 8.99 [Mn(C7H3N20 6)2 · decomposing [ \ (CH30H)4] : at >230°C brown I (35.72) (3.66) (9.26) (9.08)

-----------+~-- ---~--------- I -+-- I I ~ 2. i I I 35.75 l 3.58 9.20 I 9.11 I [Fe(C7H3N20 6) 2 · I 87 172-174 • Brown I : ' (C:IhOH),] I ' I ,, (35.66) I (3.66) (9.24) I (9.21) 1:

3. 1 I Started I 35.31 I 3.72 I 9.11 I 9. 73 [Co(C7H3N20 6)2 •

11 85 1 decomposing 1 Pink I i I

tr'Lr nm' i at 129oc I (35.48) I (3.63) (9.19) 1 (9.67) 1

I \vU.l~HJ4J -+~- I ---+--+-~-----4---~ :

1

.

4· •. Started_ 1 Deep l 34.68 ' 1 .49 I 1 l .29 !,. 12.80 i

[Cuz(C+I3N20 6 )4 • 80 : decomposmg I I , I I i t'u(C7H,Nz0r,)c· at 218oC blue ! (34.50); ( 1.38) i ( 11.15) i ( ]2_69) l I (CIJ,OH)] I I I ' i

~--------------- ----~---- - ----~ ! ---r- I l ---r-----~-: -~ : • I ; 35.01 3.48 I ).05 : 10.4) I

I [Zn( C7H 1N 70 6 )7 · 1 7 S 165-167 White I , i I

i (Cll)OH)4J I (35.11) . (3.60) i (9.10) i ( 10.62) I I I I

---- ______________ _L ________ L_ ____ ~ _____ .__L_ ___ _l~-----------------l. _____________ '

2.5.3.1 IR spectra

Selected IR spectra and their assignment for the transition metal carboxylates

have been presented in Table 2.2. A broad band in the 3500-3200cm· 1 region is

assigned to -OH stretching modes. The carboxylate group displayed two absorbance

bands one at v(OCO)a,1m 1630-1660 em 1 region and other at v(OCO)sym 1400-1470

cm- 1 region in the complexes [50]. The nitro group also displayed two absorbance

bands. The v(N02)asym and v(N02)sym bands appeared at 152 7-1545 em -I and at 1340-

1357 cm- 1 respectively in the transition metal complexes [50]. The broad band at

3500-3200 cm- 1 due to v(OH) attributable to the coordinated methanol (solvent)

molecules slowly disappeared as the solvent molecules were lost during standing the

complexes at room tempareturc on bench for ~ 48h. This indicated that the solvent

molecules are loosely bound to the central metal atom. The carboxylate stretching

39

frequency indicated it to be a bridging bidentate type rather than a monodentate type.

The difference between v(OCO)asym and v(OCO)sym (~v= 153-166) is an indication of

the bridging nature of the ligand [5ll Crystallographic data also confirmed the IR

spectral interpretation at least for two complexes (3 and 4 ). The IR of the Cu­

carboxylate compound ( 4) attracts special interest. The structure has a dimeric Cu2

unit as well as a monomeric carboxylate molecule in its molecule joined via a

N02 · .. ·0 (Fig. 2.18). The IR stretching vibrations for the -OCO group, therefore,

show two types of absorptions both are in the same frequency range but identifiably

separate. The one binding the single Cu(II) units as a bridging bidentate group, the

other also as the bridging bidentate group but bridging the Cu atoms in the Cu2

dimeric moiety.

The complexation of the carboxylate moiety to the metal atom is indicated in

the new compounds not only by the x-ray crystal structure detem1inations (for Co2T

and Cu2' ) but also by the shift of vCO of the (free) carboxylic acid group( -COOH) at

l699cm' to the -1622-1629 cm· 1 v(OCOiasym and -1458-1469cm 1 v(OCO)sym· In

addition, the v(N02Lsyrn and v(N02)sym of the ligand molecule could be assigned

unequivocally.

The shape of the v(N02) band in the spectra merits a point to be mentioned.

The band is strong and slightly broad which on closer inspection indicates that an

additional stretching frequency is present almost superimposed on it. This additional

band is most likely due to the v(N02 ) of the coordinated -N02 group. The -N02 group

is connected to form the molecule of the complex with a "Cu-carboxylate dimer" and

a mononuclear species which are not connected via bridging carboxylate ligands but

via the nitro-0 atoms .. as has been demonstrated by the X-ray crystallography (Fig.

2.18). In all other compounds of this series -N02 group stretching frequency did not

show this characteristic indicating its noninvolvement in further coordination.

2.5.3.2 Magnetic moment

The magnetic moment data are in table 2.3. The magnetic moment data

indicate an octahedral geometry for Mn(II), Fe( II) and Co( II) complexes. The

magnetic moment data correspond satisfactorily to the required values for unpaired

electrons in the compounds for an octahedral disposition around the central metal ion

40

[52]. The subnormal value of ~Lett for Cu(II) complex indicates that the coordination is

possibly octahedral around the metal atom and suggesting an antiferromagnetic spin­

exchange interaction within each molecule [53]. The magnetic moment data thus

indicates in the complex a dimeric Cu2 unit is present. The magnetic moment value of

1.49 B.M. per copper appears to be low for a d9 configuration. This suggests the

presence of a strong spin-spin interaction through the bridging ligand in the dimeric

unit [54-58] as also identified by the preliminary X-ray crystallography study.

Table 2.2 IR spectral data (cm-1) for compounds 1-5

[ Compound v(OCO)as~Tv(OCO)sym tw = fv(OH)- --~ ~(:t:To;)as;n-1 v(NOz)s~:-~

[ _ -+ _ ~~bc~~:J"-L _ I I I

~: 1 1624(s) !460(s) \164 \3446(v,b) h541(s) 1 1350(0l

l-2~ -Tt624(m)-----t 1458(s) --- ·i-166- - ·t 342I(m,b)f I54l(s)- -r_-1352(s)--1 I . I I I I J r 3. t·-i-627(w_) _____ ll462(m) --r165- .... I 3386(~,b)- -l-527(~)-11357(s)---l i , I i i ' 1

f _ +-------:-----L--------+-- --+--~------+ ~---- _ .· ... L------ ··-i I 4. 1629(m) / !467(s) 1 162 1 3356(w,b) 1 L<~6(m) 1355(s)

I I 1 1 I

I '"1655(s) I al400(s) ! I I bl545(s) 'bl340(s) i

. ------- ~ - -- _J_ - . L -~-. ------- ··- ~------ -: l622(m) [I469(m) i 153 1342\(v,b) I 1542(m)

·- ··-------······· _____ __]_ _______ ·---·· __ _j_ ______________ _j___ ______________ _L_ ____ ...

5.

s. strong: m. medium: w, weak; b, broad: v, very

weak bridging bidentate type v(OCO), b=For uncoordinated free v(N02 )

2.5.33 Differential calorimetric analysis

The Differential calorimetric analysis of 2 exhib1ted a peak at 171 56 'C. It

shows that the enthalpy at l 71.56°C i:-. \H --14. I 1 J/g. The complexes 3 and 4 on

heating ti-om 1 00-230°C underwent decomposition. The compound 3 displayed a peak

at 12)).64°C corresponding to the melting of the compound (L\l-1 --10.38 J/g).

Compound 3 after melting yielded a compound which underwent further

decomposition between 130-150°C. Compound 3 decomposes further beyond 150°C

finally to decompose at 163.93°C (;\,.II 74.12 J/g). The compound 4 also underwent

decomposition at a temperature between 148.07°(' to 218.56°C. At 21 S.56oC the

enthalpy of 4 \Vas (.:.\H ~50.31 J/g). But no infom1ation of phase change could be

4

obtained during the cooling of the compounds as because the compounds were

decomposed by then. It is likely that the compounds decomposed by giving off C02.

However, investigations on the decomposed products were not carried out in this

investigation.

2.5.3.4 Electronic Spectra

The spectral data for 1-5 are summarized in Table 2.4. Towards the visible

region, the electronic spectra showed absorptions for 3 and 4 attributable to an n -*

7r* transition within the nitro group and benzene nng chromophore owing to extensive

conjugation, which is most likely the reason for the observed spectra in methanol

solution.

Table 2.3 Magnetic moment data for compounds 1-4a

Complex Magnetic No. ofunpaired Hybridization -~ St~~eochemistry \

-1 i5~t:iliCd~ Octahedral

1.

spms

---- ----+-------------1 Octahedral

---i------··-i Octahedral l"

Hgl Co(SCN )4] as standard

Table 2.4 Electronic absorption spectra of compounds 1-5 recorded m methanol

I Compounds Amax(nm) --·1

I I rt.--------. 234,209

2. 229,214

3. 236,222, 515

-----------~-

4.

5. 232,213

----------

2.5.3.5 X-ray Crystal Structure

This section deals with the X-ray crystallographic studies of transition metal

carboxylates of 3,5-dinitrobenzoic acid Co(Il) and Cu(II). Compounds 3 and 4

provided single crystals suitable for the X-ray crystal structure determination. The

crystal structures ofthese complexes are described below.

2.5.3.5.1 Crystal Structure of Co(Il) complex of 3,5-dinitrobenzoic acid (3)

The author was able to successfully isolate suitable single crystal of 3 for X­

ray crystallography. The Co11 atom (site symmetry T) in the title complex,

[Co(C7H3N206)2(CH30H)4], exists within an octahedral 0 6 donor set defined by two

0-monodentate 3.5-dinitrobenzoate anions and four methanol 0 atoms. An

intramolecular Om-H- · ·Oc (m -"- methanol and c = carbonyl) hydrogen bond leads to

the formation of an S(6) ring. In the crystaL centrosymmetrically related molecules

associate via further Om-H · ·Oc hydrogen bonds. leading to linear supramolecular

chains propagating along the a-axis direction. The Co(II) atom in (I), (Fig. 2.16), is

located on a crystallographic centre of inversion and exists within an octahedral 0"

donor set defined by two carbox ylate-0 1 atoms and four methanoi-0 atoms. The Co-­

O 1 bond distance [(\"}-0 l ' 2.0666 (17) A] is comparable to those, i.e. 2.0525 (20)

and 2.0587 ( 19) k found in the related tetra-aqua-bis(3,5-dinitrobenzoato-

0)cobalt(II) tetrahydrate stn1cture [ 59-61]. A small disparity in the Co--Omethanol bond

distances in (I) [Co- 07 -~· 2.1094 (16) and Co--08 -' 2.0645 ( 18) A] is noted. The

methanol-07--H hydrogen forms an intramolecular 0 H- .. 0 hydrogen bond with the

carbonyl-02 atom to close an almost planar {Co-0-C-O .. ·H-0} S(6) ring, Table 2.5.

The methanoi-08--H also forms a hydrogen bond to the carbonyl-02 atom on a

centrosymmetrically related complex, Table 2.5 This results in the formation of 12-

membered { Co--0-H .. ·0-C--0 }2 synthons and linear supramolecular chains along the

a axis, (Fig. 2.17). It is noted that the packing of molecules brings into close proximity

two nitro-0 atoms, i.e. 04 .. ·04ii = 2.756 (3) A for 3-x, -y, 2-z. While the nature of this

interaction is not obvious, there are approximately 50 precedents for such Onitro· .. Onitro

contacts < 2.70 A in the crystallographic literature [62]. Table 2.6 describes the

Hydrogen-bond geometry in (A, o ) and Geometric parameters (A, 0) is presented

below.

43

Table 2.5 Selected bond lengths (A).

1 Compound 3

I ca--_o __ 7-+--2_. 1_09_4_<_1_6 )---i

I Co---08 2.0666 ( 17)

~<>--01 12.0666 (17)

Table 2.6 Hydrogen-bond geometry (A., o ) of compound 3.

1-D=If:~x- _____ D=H____ fJ::.A ---------~x- -- -~H-··A . I 07---H7o···02' 0.85 (3) ____ 1.840 ( 15) ___ 2.645 QL __ :---1s8(3) _____ J tQt-H8o .. ·02" 0.85 (3) 1.817 (1 0) 2.662 (2) 179 (3) j

Symmetry codes: (i)-x+l,-y+l, -z+l; (ii)x-l,y,z.

c:reometric parameters (A, 0) of compound 3.

Co---08 2.0645 (l8) N2 -C6 1 .47o (4) C<r--08' 2.0645 (18) Cl---C2 1.511(3) Co--Ol 2.0666 ( 17) C2 C7 1380 (3) Co-Ol' 2.0666 (16) C2- -C3 1.385 (3) Co---07 2.1094 (16) C3--C4 1.373(3) Co--07' 2.1094 (16) C3---H3 0.9300 01--Cl 1.250 (3) C4--C5 1.371 (4) 02--CI 1.247 (3) C5C6 1.378 (4) 03--Nl 1.179 (4) CS-115 0.9300 04---Nl 1.!90 (3) C6 C7 1.379 (4) 05--N2 1.220(4) C7---H7 0.9300 06--N2 1.209 (4} C8--H8A 0.9600 07---C8 1.418(3) C8-H8B 0.9600 07--H70 0.85 (3) C8-H8C 0.9600 08--C9 1.408 (3) C9---H9A 0.9600 08-H80 0.85 (3) C9-H9B 0.9600 Nl-·-C4 1.482 (3) C9-H9C 0.9600 08- Co---0 l 91.36 (8) C7--C2-C3 119.3 (2) 08i- CoOl 88.64 (8) C7- -C2 -CI 120.5 (2) 08-Co 0 I' 88.64 (8) C3 -C2--Cl 120.2 (2) 08i--Co---O l' 91.36(8) C4C3--C2 119.1 (2) 08--Co---07 88.14 (7) C4--C3--H3 120.5 08i--Co-07 91.86 (7) C2--C3-£I3 120.5 01-Co-07 89.22 (7} C5-C4-C3 123.3 (2) 0 1 i---Co--07 90.78 (7) C5-C4-Nl 119.3(2) 08-Co-07i 91.86 (7) C3-C4--Nl 117.4(2) 08i-Co-07i 88.14(7) C4--C5-C6 116.3(2) Ol--Co--07i 90.78 (7) C4--C5-H5 121.9 01 i---Co---07i 89.22 (7) C6-C5-H5 121.9 0 I --Co---0 1 i 180.0 C5-C6-C7 122.6 (2) 07- Co-07i 180.0 C5---C6-N2 119.1 (3) 08 Co--08i 180.0 C7 -C6--N2 118.3 (3)

Cl Ol -Co 130.70 (16) C6-C7-C2 119.4(2) CS- -07---Co 128.82 (16) C6---C7--I £7 120.3

44

C8-07--H70 113 (2) C2--C7-H7 120.3 Co--07--H70 105(2) 07-C8-H8A 109.5 C9-08-Co 131.57 (18) 07-C8-H8B 109.5 C9-08-H80 110 (2) H8A-C8-H8B 109.5 Co--08-H80 118 (2) 07-C8-H8C 109.5 03-NI-04 122.3 (3) H8A-C8-H8C 109.5 03-NI-C4 118.6(3) H8B-C8-H8C 109.5 04-N1-C4 119.1 (3) 08-C9-H9A 109.5 06--N2-05 123.7 (3) 08-C9-H9B 109.5 06--N2-C6 118.5 (3) H9A-C9-H9B 109.5 05-N2-C6 117.8 (3) 08-C9-H9C 109.5 02-Cl-01 126.1 (2) H9A-C9-H9C 109.5 02-C1-C2 118.0 (2) H9B-C9-H9C 109.5 Ol-Cl~-C2 115.9(2) 08--Co--0 1-C 1 87.5(2) C 1--C2--C3-~C4 179.8 (2) 08i-Co-01-C1 -92.5 (2) C2-C3-C4-C 50.0(4) 07-Co-0 1-C1 175.6(2) C2-C3-C4-N 1 179.5 (2) 07i-Co-01-C1 -4.4 (2) 03-N1-C4-C5 173.0(3) 08-Co-07-C8 125.9(2) 04-N1-C4-C5 -9.2 (5) 08i-Co-07-C8 -54.1 (2) 03-N 1-C4-C3 -6.5 (5) 01-Co-07-C8 34.5 (2) 04-N1-C4-C3 171.2 (3) 0 I i-Co--07~---C8 -! 45.5 (2) C3-C4-C5--C6 0.2 (4) 0 1--Co-08--C9 -58.0 (3) N 1--C4-C5-C6 - i 79.3 (3) 0 1 i--Co-08-~C9 122.0 (3) C4-C5-C6-C7 -0.5 (4) 07--Co--08--C9 147.1 (3) C4--C5---C6-N2 178.2 (3) 07i-- Co--08-C9 32.9 (3) 06-N2-C6--C5 177.2 (3) Co--01 -CI- 02 6.2(4) 05--N2~-C6-- -C5 3.4(5) Co--Ol Cl C2 175.42 (15) 06---N2--C6-~C7 4.0 (5) 02--Cl - C2 C7 --178.2 (2) 05---N2-C6--~C7 175.4(3) 01--Cl C2--C7 0.3 (4) C5-C6--C7--C2 0.6 (4) 02 ('\ C2---C3 1.6(4) N2~~C6-C7~--C2 17R.1 (3) 0\ Cl C2-- C3 179.9 (2) C3---C2--C7 --C6 -0.3 (4) C7 -C2 C3--("4 00(4) Cl--C2--C7-- C6 I 79.~ (2l

Symmetrycodes:(i) x+-1, v-tl. .:::~1

Supplementary data and figures for this paper are available from the lUCr electronic archives (Reference: HB534 7 ).

45

Fig. 2.16 The molecular structure of (3) extended to show the coordination geometry for the Co( II l atPm. -;howing di-.;placement ellipsoids at the 50Cif, probability level. Symmetry qperationi: l r. I-\, l-:,

Fig. 2.17 Linear supramolecular chain along the a axis in (3) mediated by 0-H·"O hydrogen bonding. These and the intramolecular 0-H .. ·O hydrogen honds are shown a'> hlue dashed line:-..

46

2.5.3.5.1 Crystal Structure of Cu(II) complex of 3,5-dinitrobenzoic acid ( 4)

The author was able to successfully isolate suitable single crystals of 4 for X-ray

crystallography. The preliminary analysis of the X-ray crystallography studies of 4

reveals that the complex contains the asymmetric unit comprises two Cu centers, three

carboxylates, a coordinated methanol molecule and half a solvent methanol molecule.

These connect to form a ""Cu carboxylate dimer" and a mononuclear species which are

connected via bridging carboxylate ligands but via the nitro-0 atoms (Fig. 2.18 l and

overall. a 2-D array is formed (Fig. 2.llJJ. The details of the bond angles and bond

distances are not available at the moment.

Fig. 2.18 X-ray crystallography structure of the asymmetric unit of cornpounc14.

47

Ftg. 2. '" 19 A 2-D array o f compound 4.

48

Fig. 2.20 Crystal packing structure of compound 4.

\;

2.5.4 Biological properties of transition metal carboxylates of 3,5-dinitrobenzoic acid.

2.5.4.1 Anti-fungal activities

The antifungal properties of the transition metal carboxylates 2-4 are

summarized in table 2.5. The fungitoxic effect of the transition metal carboxylates

were screened at three concentrations 25, 50 and 100 ppm, on spore germination of

two different pathogens of mango (L. theobromae ) and tea (C. eragrostidis ). The

results showed that 4 was most active followed by 3 against the tested fungal strains.

Copper fungicides in potentiality are comparable to organtin compounds, such as

triphenyltin acetate and triphenyltin hydroxide [63]. The compound 4 markedly

inhibit the spore germination of each of the above fungi at concentrations above 50

ppm. ;~.t 100 ppm, almost complete inhibition of spore germination ensued,

irrespective of the pathogen, which indicates high fungitoxicity against different

groups of pathogen.

Table 2.5. Spore gennination (r'l'o) of L theohromac and C. l:'ragrostidi.'> tn the

presence of compounds 2--4.

Chemicals Spore genmnatwn u1 rl ot Spore germination °i() of

L. theohromae. C. eragrostidis

Cone (ppm) Cone (ppm)

25 50 100 25

84.0 7R.5 68.3 86.6 79.2 67.1 i +. ·····--·-- .. ' .. ·- .. -- ... t.. " ---T·-· ----·--- ·---- --· ______ _. __ . __ _

81.2 I 49.3 i 2.J.4 79.3 ' 48.3 II 21.4

r-4-::-.----,----1----1-4._1 -~~I ~t--u--+------12 ___ 2 -t 5.7 _ 2.5

Control 87 92

3.

(water)

50

2.5.4.2 Phytotoxic properties

The phytotoxic effects of transition metal carboxylates were studied on

economically important crop Oryzae sativa (Khitish). The phytotoxic effects of

compounds 2-4 as a function of the concentration are summarized in Table 2.6. The

results indicate that none of the transition metal carboxylates displays any inhibitory

effect on seed germination.

Table 2.6 Phytotoxicity of compounds 2--4, after seed treatment of Indian nee

( Oryzae sativa), cultivar Khitish.

~'compound 1 Percentage(%) of

i seed germination after

j4h treatment

f---------------·-------·-----' Cone. (ppm)

2.

3.

I Percentage (%) of I r1 . . ft l seeu germination a ~er

I 8h treatment

Cone. (ppm)

~----

\ Percentage (%) of l ' I f seed germination after 1

1.

I ~ I

1 12h treatment 1

I I --'-··· "---------------- '"""' J

I ! Cone. (ppm)

J 00 I 25

The control seeds were incubated in methanol/water (I :5) for the indicated period.

51

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